Abivax shares tumble on Phase 3 trial data

Abivax released topline results on June 1–2, 2026 from its Phase 3 ABTECT maintenance trial of obefazimod in adults with moderately to severely active ulcerative colitis. The late stage data immediately drew attention from both clinicians and investors, given obefazimod’s potential role in inflammatory bowel disease treatment.

The ABTECT maintenance study followed patients over 44 weeks and evaluated once daily oral dosing of obefazimod at 25 mg and 50 mg compared with placebo. A total of 580 patients were included in the maintenance population, providing a substantial sample to assess longer term efficacy and safety.

Abivax reported that both obefazimod doses met the primary endpoint at Week 44. Clinical remission was achieved in 50.8% of patients receiving 25 mg and 51.3% of those on 50 mg, compared with 10.4% in the placebo group. Placebo adjusted differences were 39.3% for 25 mg and 40.3% for 50 mg, with p values below 0.0001.

Beyond the primary endpoint, the company said all key secondary endpoints were met across the 580 patient maintenance cohort. These topline results indicate robust and sustained treatment effects over the 44 week maintenance period in moderately to severely active ulcerative colitis.

Abivax described the overall 44 week safety profile of obefazimod as favorable, reporting no new safety signals and no deaths in the trial. Treatment emergent adverse event rates were 50.0% for placebo, 58.0% for the 25 mg group and 71.8% for the 50 mg group over the study period.

Within the higher 50 mg dose arm, three malignancy cases were observed: one prostate cancer, one breast cancer and one colonic dysplasia. Investigators considered these cases unrelated to obefazimod treatment. Nonetheless, these cancer findings became a focal point for market reaction after the data release.

Following publication of the topline ABTECT maintenance results, Abivax shares fell sharply. The stock declined as much as 32% intraday on June 2, 2026, reflecting investor concerns centered on the safety data despite the strong efficacy outcomes.

Abivax reiterated that it intends to advance obefazimod toward regulatory review. The company said it plans to submit a New Drug Application to the U.S. Food and Drug Administration for obefazimod in ulcerative colitis in late Q4 2026 and held a conference call to discuss the topline maintenance data and next steps.

The combination of high clinical remission rates, achievement of all key secondary endpoints and the reported overall favorable safety profile underscores obefazimod’s potential in ulcerative colitis maintenance therapy. At the same time, the malignancy cases in the higher dose group, though deemed unrelated by investigators, highlighted the sensitivity of investors to any cancer related findings in long term trials.

As Abivax prepares for its planned NDA submission in late Q4 2026, the ABTECT maintenance data will frame ongoing discussion among regulators, clinicians and investors around the balance of efficacy and safety for obefazimod and its prospective role in treating moderately to severely active ulcerative colitis.